OPA656: OPA656

Hi Michael

This is new thread related to OPA656. Here you please try to insert the snips. 

I was really not working on this one anymore, but I was intrigued by the JFET Kai had mentioned, the ON semi 2SK2394 and pulled that into a TINA file, here is a source follower sim where it shows about 0.8nV voltage noise, 

And then the unity gain frequency response through this stage, this is what is giving you the bootstrap function, 

over 500MHz BW according to this, 

And then the file, I think - this new update is giving me problems, but here I will try to insert the V9 file for this in case anyone wants to run sims with that JFET, 

No, I can't find how to do that, I sent the file to Hasan, maybe he will insert it.

Attaching Michael's source follower sim. File must be a zip and can be dragged and dropped to the text field now. 

2SK2394 source follower.zip

Best,

Hasan Babiker

Hi Michael, hi Hasan,

the direct download is working now :-)

2SK2394 source follower.TSC

Kai

You mean instead of dragging and dropping a zip version? Exactly how did you do it? If I open insert, still doesn't look right

Click with the left mouse button on "Upload".

Kai

Your simulation with the 2SK2394 looks good :-)

I did some simulations when using a source resistor:

michael_2sk2394.TSC

Kai

7776.2SK2394 source follower.TSC

I see, you hit insert at the bottom, then upload, then on the file explorer you select the file

I had tried some resistor biasing also to reduce the quiescent in the JFET - just shifts the VGS voltage which is ok in the bootstrap if you have that isolating C to the diode bias, doesn't change the overall noise hardly at all in the full schematic since that is dominated by the large feedback R. 

Yes, works :-)

Yes, you are right, of course. Was just curcious to see what happens when using a source resistor.

Kai